DoD and its contractors process millions of pounds of energetic materials into a final usable formulation and load them into billions of items per year. This requires the use of hazardous materials and solvents in the manufacture and LAP of formulations for primary explosives, conventional ammunition, gun propellants, rocket and missile propellants, and pyrotechnics. Solvents generally are not incorporated in the final formulation, but are used in mixing materials to reduce viscosity of formulations or reduce dust for better processability, with the solvent evaporated off from the final product.
The current manufacturing base relies on processes that require workers to handle material or be in close contact with the formulations at different stages throughout the final formulation and LAP process. Many of the solvents have a high vapor pressure, which increases the likelihood of worker exposure through inhalation. Personal protective equipment and proper ventilation systems may be necessary to maintain compliance with current safe workplace occupational exposure levels. In addition, many of the solvents are flammable and require additional safety measures in the processing facility. Residual solvent in formulations has been linked to fire incidents during training exercises. Solvent containment, solvent recycling, and solventless processes have been evaluated in the past with varying success. Many alternatives have proven to be more expensive or do not meet final performance requirements.
Common solvents used in energetics manufacturing include methylene chloride (castable rocket propellants), ethyl ether, ethyl acetate, acetone and ethanol (gun propellants and pyrotechnics). These materials can be respiratory and skin irritants with acute toxicity effects, and methylene chloride is classified by the EPA as a probable cancer causing agent. Waste solvent must be handled as a hazardous waste and most require additional reporting requirements for use and release. Nitric acid, commonly used as the primary nitrating agent for many energetic materials including propellants, is also used as a key carrier solvent in energetic manufacturing. Excess nitrates can lead to significant waste in the production process.
Water is commonly used as a solvent for mixing in pressable formulations. While water is an environmentally preferable solvent, this water must be treated prior to release in the environment and the clean-up process to remove residual energetic materials completely can be difficult and energy intensive. Water is typically used in excess, and a large influx of water can strain wastewater treatment facilities. This makes it more difficult to remove all residual energetics from the water and increases the risk of releasing potentially regulated materials into the environment.
